Pneumatic motor assembly for a lubricant pump

ABSTRACT

A pneumatic motor assembly for a lubricant pump comprises a body which forms a cavity supplied with compressed air, a first hole and a second hole which are formed axially on the side wall of the cavity, a stem, which is slidingly accommodated in the first and second holes and supports, at one end, a piston which moves in a cylinder associated with the body and, at the other end, cooperates with the riser of the pump. An exchanger means is accommodated in the cavity and is provided with an axial through hole which slidingly accommodates a narrow intermediate portion of the stem; a means for diverting the air is associated with a front opening of the cavity and interacts with the exchanger means; and an elastic means cooperates laterally with the exchanger means; the axial through hole includes a wider end portion, which is directed toward the end of the stem that is provided with the piston and accommodates a non-narrow part of the stem during the return stroke of the piston; the elastic means is arranged between the exchanger means and the side wall.

[0001] The present invention relates to a pneumatic motor assembly for alubricant pump, which is used particularly in the field of maintenanceand repair of vehicles such as cars, vans, trucks, tractors, et cetera.

[0002] The background art is constituted by a pneumatic motor assembly,for lubricant pumps, comprising a body that forms a cavity supplied withcompressed air. A first hole and a second hole are formed axially in theside wall of the cavity. The holes slidingly accommodate a stem. Thestem supports, at one end, a piston that moves in a cylinder that isassociated with the body and cooperates, at the other end, with theriser of the pump An exchanger means is accommodated inside the cavityand is provided with an axial through hole, which slidingly accommodatesa narrow intermediate portion of the stem. The exchanger meanscooperates frontally with a means for diverting the air, which isassociated with a front opening of the cavity and is laterallyassociated with an elastic means. In particular, the cooperation betweenthe exchanger means and the elastic means is provided by two levers,which are pivoted between the side walls of the body and the front facesof two bushes slidingly inserted in holes provided laterally in thebody. The elastic means acts on the rear faces of the bushes and isconstituted by two spiral springs. The springs are accommodated in twocaps, which are screwed by virtue of one end to the holes formedlaterally in the body.

[0003] The operation of such motor assembly is as follows. Assume, forexample, that the piston is performing its forward stroke inside thecylinder. Initially, the exchanger means is in a retracted position. Theair is introduced in the cylinder so as to move the piston through ahole provided to the rear in the cavity, the diverting means and apassage that runs within the body and leads to the bottom of thecylinder. Correspondingly, the air contained in the chamber, whosevolume is gradually reduced by the piston, is discharged externallythrough the diverting means. The exchanger means moved by the stemreaches the inversion position from the retracted position, and fromthat position it is moved to the forward position by the intervention ofthe elastic means. In this transfer, the exchanger means acts on thediverting means so as to block the intake and outlet, preparing them forthe return stroke of the piston. In this case, the air is introducedthrough the usual hole, the diverting means and the pipe for connectionto the top of the cylinder. Correspondingly, the air contained in thechamber, whose volume is gradually reduced by the piston, is dischargedexternally through the passage and the diverting means. The exchangermeans, entrained by the stem, again reaches the inversion position fromthe forward position. From the inversion position it is moved to theretracted position by the intervention of the elastic means. During thistransfer, the exchanger means acts on the diverting means so as to blockthe intake and the outlet, preparing them for the new forward stroke ofthe piston, and so forth. The reciprocating movement of the stemaspirates the lubricant, which by rising up the riser becomes availablefor dosage.

[0004] The main drawback of the above described motor assembly is itsperformance, which is highly impaired by the fact that the strokeavailable inside the cylinder is not utilized completely by the piston.In fact, during the return stroke, the piston stops before it reachesthe bottom of the cylinder. This is due to the fact that the narrowportion of the stem is necessarily longer than the exchanger means.Therefore, during the forward stroke of the piston, the narrow portionof the stem protrudes partially with respect to the bottom of thecylinder. Accordingly, it is necessary to prevent the variation indiameter that occurs between the narrow portion and the rest of the stemthat lies outside the bottom from interfering with the annular gasketarranged so as to wrap around the stem on a guiding and sealing bushassociated with the first hole of the cavity that is directed toward thecylinder. For this reason, a bush of considerable height is currentlyused and in turn prevents the piston from reaching the bottom at the endof its return stroke. Furthermore, within the scope of this maindrawback it is noted that this actuation of the cooperation between theexchanger means and the elastic means is particularly complicated andtherefore expensive. Moreover, the lateral protrusions formed by thecaps worsen the overall aesthetic appearance of the assembly.

[0005] A second drawback of conventional devices is that they comprise ameans, for guiding and sealing the stem toward the riser, constituted bya guiding bush, an annular gasket and a closure flange, packed andinserted in a compartment formed axially in the body, just below thecavity, and retained by an elastic end ring engaged in the compartment.Accordingly, the lubricant delivery hole is provided just below thecompartment. This entails that the axial dimension of the body isparticularly large. Since the body is normally made of aluminum, amaterial that is notoriously valuable and therefore expensive, thepurchase costs of the raw material are rather onerous and have aconsiderable effect on selling prices of the end products.

[0006] Furthermore, the number of machine-tool treatments required toobtain the finished assembly is particularly large, thus increasingproduction costs. The body of the assembly is in fact obtained from asolid cylindrical block, which is initially provided with an axial borehaving different diameters and so forth, accordingly also entailingconsiderable machining waste.

[0007] The aim of the present invention is to overcome the drawbacksnoted in the prior art, by providing an improved pneumatic motorassembly for a lubricant pump that in particular improves appreciablythe operating efficiency and reduces its manufacturing costs in relationto the material used and to the number of machining treatments required,so as to contain the final cost.

[0008] Within this aim, an object of the invention is to provide a motorassembly that is highly compact.

[0009] This aim, this object and others that will become better apparenthereinafter are achieved by a pneumatic motor assembly for a lubricantpump as claimed in the accompanying claims.

[0010] Further characteristics and advantages of the invention willbecome better apparent from the description of a preferred embodimentthereof, illustrated only by way of non-limitative example in theaccompanying drawings, wherein:

[0011]FIG. 1 is a perspective view of a lubricant pump provided with theassembly according to the invention;

[0012]FIG. 2 is a partially sectional exploded view of the assembly;

[0013]FIG. 3 is a sectional view, taken along the line III-III of FIG.2, of a detail of the assembly;

[0014]FIG. 4 is a sectional view, taken along the line IV-IV of FIG. 2,of another detail of the assembly;

[0015]FIG. 5 is a sectional view of the assembly, taken along a meridianplane that passes through its longitudinal axis;

[0016]FIG. 6 is a detail sectional view of the assembly, taken along ameridian plane that passes through its longitudinal axis;

[0017]FIG. 7 is a detail sectional view, taken along the line VII-VII ofFIG. 6, of the assembly in the unassembled condition;

[0018]FIG. 8 is a detail sectional view, taken along the line VII-VII ofFIG. 6, of the assembly in the assembled condition.

[0019] With reference to the accompanying figures, and initially to FIG.1, the pump, generally designated by the reference numeral 6, is appliedvertically to a drum 7 containing liquid or semisolid lubricant.

[0020] The pump 6 is substantially axially elongated and includes, inthe following order, a pneumatic cylinder 8, a motor assembly 9, and ariser 10.

[0021] The riser is rigidly associated with the lid 11 of the drum 7.

[0022] The pump 6 receives compressed air through a hose 12 anddispenses the lubricant through a hose 13, which has, at its free end, adosage gun 14 that can be operated manually.

[0023] The motor assembly 9 includes a body 15 that is predominantlyaxially elongated.

[0024] The body 15 forms a cylindrical cavity 16, which liesapproximately at right angles to the length of the body 15. The cavity16 is fed with compressed air through a hole provided at the rear (notshown) for connection to the hose 12.

[0025] A first hole 18 and a second hole 19 are provided on the sidewall 17 of the cavity 16, along the main axis of the body 15.

[0026] A stem, generally designated by the reference numeral 20, slideswithin the holes and supports, at one end, a piston 21, which movesinside the cylinder 8 and cooperates with the riser 10 at the other end.

[0027] The stem 20 is formed in two portions 22 and 23, which aremutually joined by virtue of a screw coupling.

[0028] An exchanger means 24 is accommodated inside the cavity 16 and isprovided with an axial through hole 25, which slidingly accommodates anarrow intermediate portion 26 of the stem 20.

[0029] The narrow intermediate portion 26 is formed in the end part ofthe portion 22 that lies opposite to the one provided with the piston21.

[0030] At the end of the narrow intermediate portion 26 there is a shortthreaded part 27, which is engaged in a corresponding complementarilythreaded hole 28 formed at the end of the portion 23, so as to form thescrew coupling.

[0031] An elastic means, generally designated by the reference numeral29, cooperates laterally with the exchanger means 24 by virtue of levers30 engaged in slots 31 formed on the side wall of the exchanger means24.

[0032] A diverting means D introduces air from the cavity 16 first intoone chamber of the cylinder 8 and then into the other chamber, thechambers being formed by the piston 21, and evacuates externally the aircontained alternately in each one of the chambers, whose volume isgradually reduced by the piston 21.

[0033] The diverting means D is associated with a front opening of thecavity 16 and interacts with the exchanger means 24 by virtue of a flatregion 32 formed at the front on the exchanger means.

[0034] The particularity of the motor assembly 9 is that the axialthrough hole 25 comprises a wider end portion 33, which is directedtoward the end of the stem 20 that supports the piston 21 so as toaccommodate a non-narrow part of the stem 20 during the return stroke ofthe piston 21, thus delaying the exchange.

[0035] In this manner, the stroke of the piston shifts toward the returnto an extent that is equal to the depth of the wider portion 33.

[0036] As shown in particular in FIG. 5, by virtue of the wider portion33 the stem 20 in fact penetrates more deeply into the exchanger means24.

[0037] Again with reference to FIG. 5, the non-narrow part, designatedby the reference numeral 34, is located directly behind the narrowportion 26 in the direction of the return stroke of the piston 21.Accordingly, the length of the non-narrow part 34 is equal to the depthof the wider end portion 33.

[0038] The limit of the return stroke of the piston 21 is determined bythe locator 35, which is formed between the wider end portion 33 and theaxial through hole 25, which constitutes an abutment with respect to thecorresponding locator 36 formed on the stem 20 so as to straddle thenarrow intermediate portion 26 and the non-narrow part 34.

[0039] The above feature allows to use a guiding and sealing bush 37associated with the first hole 18 which has a limited height, so as tonot interfere with the return stroke of the piston 21.

[0040] Furthermore, such feature allows to avoid the problem of theescape of the locator 36 from the gasket 38 provided on the guiding andsealing bush 37, although the bush has a limited height. The locator 36in fact always lies behind the conventional assemblies during theforward stroke of the piston 21, and for this reason it does notinterfere with the gasket 38. The base of the guiding and sealing bush37 acts as an abutment for the exchanger means 24 in the advancedposition.

[0041] For a good operation of the assembly 9, it is also necessary toprovide a slight elongation of the exchanger means 24 on the partdirected toward the riser 10. This ensures a sufficient resting surfacebetween the exchanger means 24 and the stem 20 during mutual sliding.Accordingly, the narrow intermediate portion 26 is also extended by thesame length, so as to restore the proportions between the axialdimensions of the components that interact.

[0042] With the exchanger body 24 and the stem 20 thus modified, theother locator 39 formed on the stem 20 would interfere with the guidingand sealing means used on the side of the riser 10 in conventionaldevices. Therefore, it would be necessary to further lengthen the body,but this would entail obvious new increases in the costs of rawmaterial.

[0043] In order to obviate all this, the assembly 9 includes a guidingand sealing cartridge 40, which is engaged in the second hole 19,protrudes along the stem 20 outside the body 15, and is directed towardthe riser 10.

[0044] The cartridge 40 is formed by a first tubular segment 41, whichis provided externally with a threaded end part 42, which is engaged inthe corresponding second complementarily threaded hole 19, and isprovided internally with a likewise threaded intermediate part 43. Thehead of the first segment 41 acts as an abutment for the exchanger means24 in the retracted position.

[0045] A second shorter tubular segment 44 is arranged coaxially insidethe first tubular segment 41 and is externally provided with a threadedend part 45, which engages the corresponding threaded intermediate part43 of the first tubular segment 41.

[0046] Internally, the second tubular segment 44 has, at the threadedend part 45, a hexagonal seat 46, which accommodates a handling tool(not shown) for screwing and, at the opposite end, has an annular gasket47, which is adapted to form a seal on the portion 23 of the stem 20against air seepage from the cavity 16 toward the riser 10.

[0047] In order to avoid seepages of lubricant in the oppositedirection, an annular gasket 48, having an inverted U-shapedcross-section, is inserted in the first tubular segment 41 on the sideof the riser 10, just below the second tubular segment 44.

[0048] Also, in order to avoid any wavering of the piston 21, at thebeginning of its forward stroke, it is possible to provide a secondarychamber 49 formed in the bottom of the cylinder 8.

[0049] With particular reference to FIGS. 6, 7 and 8, an elastic means,generally designated by the reference numeral 130, cooperates laterallywith the exchanger means 24 as a replacement of the conventional meansshown in the other figures. A particularity of the elastic means 130 isthat it is arranged between the exchanger means 24 and the side wall 17.The elastic means 130 is constituted by two springs 131, shown in FIG.7.

[0050] Each spring 131 includes two legs 132, two arms 133, and acentral concavity 134, which in the active condition is directed intothe cavity 16.

[0051]FIG. 7 shows that, before assembly, the legs 132 are divaricated,whereas after assembly the legs 132 are substantially parallel.

[0052] Accordingly, before assembly, the legs 132 form an obtuse anglewith the arms 133 and in the active condition they form a substantiallyright angle.

[0053] The legs 132 of each spring 131 are inserted in seats 135 and 136formed respectively in the exchanger means 24 and in the body 15.

[0054] More specifically, the seats 135 formed in the exchanger means 24include two holes 137 in which elastic pins 138 are inserted.

[0055] The holes 137 are formed in the sides of the exchanger means 24in the central area of the flat region 32, symmetrically and at rightangles to the longitudinal central axis of the exchanger means 24.

[0056] The seats 136 formed in the body 15 include two holes 139, inwhich elastic pins 140 are inserted.

[0057] The holes 139 are formed on the margin of the cavity 16, in thecentral band of the body 15, symmetrically and at right angles to thelongitudinal central axis of the body 15.

[0058] The holes 139 include a first portion 141 and a second portion142. The first portion 141 of the holes 139 has a larger diameter thanthe second portion 142.

[0059] In this manner, during the drilling of the holes 139 straightgrooves, equal in length to the first portions 141, are formed on theside wall 17, allowing to position the springs 131.

[0060] The springs 131 are kept in position by pins 143, inserted in thefirst portions 141 after the springs 131 have been arranged in theactive position.

[0061] The pins 143 are in turn retained within the first portions 141by the diverting means D, which closes the front opening of the cavity16.

[0062] The springs 131 are preferably made of a metal wire shaped so asto lie on a plane.

[0063] With reference to the accompanying figures, the general operationof the assembly 9 is per se known.

[0064] The operation of the elastic means 130 occurs as follows. Assumethat the exchanger means 24 is in one of the two stroke limit positions.Moving from this position, the exchanger means 24 compresses the springs131 until it reaches the position in which the diverting means Dreverses the flow of the circulation of the air. From this position, thesprings 131 are released, pushing the exchanger means 24 to the otherstroke limit position, and so forth.

[0065] As described above, the improved pneumatic motor assemblyachieves the intended aim and object, allowing an actual improvement inefficiency owing to the fact that the stroke available in the cylinderis utilized fully by the piston, both during the forward stroke andduring the return stroke, and it allows to reduce manufacturing costsand accordingly the final price, and to improve its overall aestheticappearance.

[0066] Furthermore, the guiding and sealing cartridge external to thebody allows a considerable saving of material thereon which isapproximately equal to 20%, because the portion of body related to thecompartment for accommodating the means for guiding and sealing the stemon the riser side is no longer necessary, and because the lubricantdispensing hole is formed directly below the cavity instead of below theguiding and sealing means.

[0067] The same solution allows to use tubular segments instead of solidcylindrical segments in order to form the body. This feature allows tosave on the purchase of raw material and allows a considerable reductionin the number of operations of the manufacturing cycle.

[0068] For example, it is noted that the first and second holes have thesame diameter and are equally threaded.

[0069] Furthermore, according to the invention, it becomes possible touse a single body for a wide variety of pumps.

[0070] The solution adopted to provide the seats helps to reduce costs.Instead of providing very small holes in order to insert the legs of thesprings, it is in fact more convenient to provide holes having a largerdiameter and then insert therein elastic pins so as to bring the holesto the required diameter. The solution chosen for fitting the springs isalso relevant, since it proves itself very easy. It is in factsufficient to place the body at the end of its stroke, take each springby compressing its legs until they are parallel, and then insert them inthe already-provided seats.

[0071] In practical execution, the materials used, the shapes, thedimensions and the constructional details, may be different from theones described herein but technically equivalent thereto without therebyabandoning the scope of the invention.

1. A pneumatic motor assembly for a lubricant pump that comprises abody, which forms a cavity supplied with compressed air, a first holeand a second hole formed axially on the side wall of said cavity, astem, slidingly accommodated in said holes and supporting, at one end, apiston moving in a cylinder associated with said body and, at the otherend, cooperating with the riser of said pump; an exchanger means,accommodated in said cavity and provided with an axial through holeslidingly accommodating a narrow intermediate portion of said stem; ameans for diverting said air, associated with a front opening of saidcavity and interacting with said exchanger means, and an elastic meanswhich cooperates laterally with said exchanger means, characterized inthat said axial through hole comprises a wider end portion, directedtoward said end of said stem that is provided with said piston andaccommodating a non-narrow part of said stem during the return stroke ofsaid piston; and in that said elastic means are arranged between saidexchanger means and said side wall.
 2. The assembly according to claim1, characterized in that said non-narrow part is located directly behindsaid narrow portion along the return stroke of said piston.
 3. The motorassembly according to one or more of the preceding claims, characterizedin that said exchanger means comprises a locator formed by said widerend portion and by said axial through hole, said locator forming anabutment for the corresponding locator formed on said stem astride saidnarrow portion and said non-narrow part.
 4. The motor assembly accordingto one or more of the preceding claims, characterized in that saidexchanger means comprises an extension toward said riser and in thatsaid narrow intermediate portion comprises an extension equal to saidextension of said exchanger means.
 5. The motor assembly according toone or more of the preceding claims, characterized in that it comprisesa guiding and sealing bush, screwed into said first hole and protrudingmoderately into said cylinder so as to not interfere with said returnstroke of said piston.
 6. The motor assembly according to one or more ofthe preceding claims, characterized in that it comprises a guiding andsealing cartridge, rigidly coupled to said second hole and protrudingalong said stem outside said body toward said riser.
 7. The motorassembly according to one or more of the preceding claims, characterizedin that said cartridge comprises a first tubular segment, externallyprovided with a threaded end part that engages said secondcomplementarily threaded hole and is internally provided with a threadedpart.
 8. The motor assembly according to one or more of the precedingclaims, characterized in that said cartridge comprises a second tubularsegment, internally coaxial to said first segment, and shorter than saidfirst segment, said segment being externally provided with a threadedend part that engages in said complementarily threaded part of saidfirst segment and is internally provided, at said threaded end part,with a hexagonal seat for accommodating a handling tool for screwingsaid second segment into said first segment, and is provided, on theside of said riser, with an annular gasket for providing a seal on saidstem against seepages of air from said cavity to said riser.
 9. Themotor assembly according to one or more of the preceding claims,characterized in that said cartridge comprises an inverted U-shapedannular gasket, inserted in said first segment on the side of said riserjust below said second segment and preventing seepages of lubricant fromsaid riser into said assembly.
 10. The motor assembly according to oneor more of the preceding claims, characterized in that it comprises anannular secondary chamber formed in the bottom of said cylinder.
 11. Themotor assembly according to claim 1, characterized in that said elasticmeans comprises a pair of springs.
 12. The motor assembly according toclaim 11, characterized in that each one of said springs comprises twolegs, two arms and a central concavity directed toward said cavity. 13.The motor assembly according to claim 12, characterized in that beforeassembly said two legs are divaricated and in the active condition saidtwo legs are substantially parallel.
 14. The motor assembly according toclaim 12, characterized in that before assembly said two legs and saidtwo arms form an obtuse angle and in that in the active condition saidtwo legs and said two arms form a substantially right angle.
 15. Themotor assembly according to claim 12, characterized in that said legsare inserted in seats formed respectively in said exchanger means and insaid body.
 16. The motor assembly according to claim 15, characterizedin that said seats of said exchanger means comprise two holes and twoelastic pins inserted in said pair of holes.
 17. The motor assemblyaccording to claim 16, characterized in that said holes in saidexchanger means are formed in the central area of a flattened region, ina symmetrical position and at right angles to the longitudinal centralaxis of said exchanger means.
 18. The motor assembly according to claim15, characterized in that said seats of said body comprise two holes,each divided into a first portion and a second portion, and two elasticpins, inserted in said second portions of said holes.
 19. The motorassembly according to claim 18, characterized in that said first portionhas a larger diameter than said second portion.
 20. The motor assemblyaccording to claim 18, characterized in that said holes in said body areformed in the central band of said body, symmetrically and at rightangles with respect to the longitudinal central axis of said body. 21.The motor assembly according to claim 19, characterized in that saidfirst portions of said holes affect said side wall so as to formstraight grooves which allow to insert said springs in said pinsinserted beforehand in said second portions.
 22. The motor assemblyaccording to one or more of the preceding claims, characterized in thatsaid springs are held in position by two pins inserted in said firstportions, said pins being in turn held in position by said divertingmeans.
 23. The motor assembly according to one or more of the precedingclaims, characterized in that said springs are formed by at least onewire shaped so as to lie on a plane.